[Note: The full text PDF of this article is available free HERE. It reviews research suggesting that up-regulation of the ‘kynurenine pathway’ may play a role in the clusters of signs and symptoms that predominate in ME/CFS and fibromyalgia patients.

What is the kynurenine pathway? It’s complex, but we located this brief video by biochemist Wesley Hurrell which diagrams the pathway; how its chronic up-regulation may lead to tryptophan and serotonin depletion & produce chronic Th1-immune activation; and the association with symptoms common in ME/CFS and fibromyalgia, including IBS, cognitive impairment, sleep disturbances and depression.]

Abstract:
Last century there was a short burst of interest in the tryptophan-related disorders of pellagra and related abnormalities that are usually presented in infancy.1,2 [L-Tryptophan is an essential amino acid that is a precursor to many neurotransmitters and neurochemicals, including serotonin and melotonin.]

Nutritional physiologists recognized that a severe human dietary deficiency of either tryptophan or the B group vitamins could result in central nervous system (CNS) sequelae such as ataxia [lack of muscle coordination], cognitive dysfunction and dysphoria [anxiety/restlessness], accompanied by skin hyperpigmentation.3,4

The current paper will focus on the emerging role of tryptophan in chronic fatigue syndrome (CFS) and fibromyalgia (FM).

The many problems related to kynurenine are just one of the problematic issues with tryptophan.

This research paper seems to insinuate that tryptophan itself isn't a problem (inferred from observed effects of an endogenous tryptophan deficiency), but primarily the chronic release of kynurenines. However, serotonin, for which tryptophan is its precursor, has been shown to be involved in numerous disease conditions, from brain degeneration, cancer, cardiovascular events, and many others (see http://www.supplements-and-health.com/tryptophan-side-effects.html). This doesn't indicate that the loading of tryptophan or serotonin, with drugs or dietary supplements, is biologically desired.